A single-tone carrier frequency, at 2.00000000000 GHz carries no information. It is a single tone and all
we can get from receiving it is the fact that it exists. In order to superimpose the voice, video, or data on
top of it, we need to change it a bit, and there are many different ways of doing this. The first and most
simple is amplitude modulation (we change its amplitude depending on the amplitude of the base-band)
called AM. The second and easy one is frequency modulation (we change its phase depending on the
amplitude of the base-band) called FM. We all know AM and FM from the radio stations. Both of these
modulations are called “analog modulation” techniques since an analog base-band transfers to an analog
control of the amplitude or frequency of the carrier frequency. These two techniques are quite easy to do,
but are spectral inefficient, that is, the spectrum around the carrier frequency takes too much frequency
space to transmit a small bandwidth of base-band information! Also, they are quite sensitive to noise and
one must have a good signal-to noise ratio (SNR) to receive AM signals (and FM signals) with clarity.